Relay



Aug. 15, 1933. 1,922,422,

H. C. DOANE RELAY Filed Aug. 22, 1930 j @ma 3/ 32 62 23 me/H4901:

Patented Aug. l5, 1933 RELAY Harry C. lDoane, lFlint, Mich., assigner toGeneral Motors Corporation, Detroit, Mich., a @orporation of DelawareApplication August 22, 1930. Serial No. 477,048

9 Claims.

This invention relates to current regulators for current controllingdevices, and has among its objects to provide a device that willsafeguard the working circuit or circuits of the accessories about anautomotive vehicle.

A further object of the invention is to provide a current limiting relaydevice that will be responsive to over-loads impressed upon a circuit,so as to reduce source depletionand fire hazard.

It is a further object of the invention to provide a device of the classdescribed, in which contacting elements are maintained in cleanelectrical condition and thus contributory to efcient operation.

A further object of the invention is to provide means for cleaning theelectrical contacts, and for varying the conductive engagementtherebetween.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing, wherein a preferred embodiment of one form of the presentinvention is clearly shown.

In the drawing:

Fig. l is a plan View of a current limiting device involving theinvention.

Fig. 2 is a wiring diagram illustrating the application of the improvedrelay in the work circuit of an automotive vehicle.

Fig. 3 is a longitudinal section of the current limiting devicesubstantially as indicated by the line and arrows 3-3 of Fig. l.

Fig. 4 is an end elevation of the same substantially as indicated by thearrow 4 of Fig. 3.

Fig. 5 is a side elevation of the current limit-z ing devicesubstantially as indicated by the arrow 5 of Fig. 4, and illustratingcertain parts thereof in a shifted position from that illustrated inFig. 3.

With particular reference to the drawing, 20 indicates a mountingbracket apertured at 21 for securing the same to any desirable support,and carries a nonconducting plate 22 by rivets 23, which plate providesa foundation for the current limiting device thereto attached. Along oneside of the foundation plate 22 is secured a plurality of terminalbrackets 25, 26 and 27 that provide for various electrical connectionsfor various parts of the device, as will presently appear. All of thework device may be connected with leads secured to the clips by one ormore of the terminal screws 28 with lock washers 29. Facilitatingelectrical connection between the members 25 and 26 there is provided aconnecting bar or bridge member 30 with a centrally disposed terminalscrew as is illustrated in Fig. 1. Aside from the extent noted, each ofthe terminal brackets are insulated from each other and from othercontributing elements of the structure.

On the insulating member 22 there is secured .60

a bracket member 31 by rivets 32, that aids in supporting anelectro-magnet device 40 by screws 33 driven into one leg thereof. Tliebracket 3l is extended and offset to form a terminal bracket 34 carryingthe screw devices 35, substantially 65 as illustrated in the drawing.The electromagnet 40comprises the form illustrated in the drawing andcomprises in main a U-shaped magnet frame 4l having the parallel legs 42and 43, joined by the bridge piece 44, and centrally apertured toreceive and retain a cylindrical pole piece 45. On the bridge piece 44there is secured an insulating disc 46 that supports a contactsupporting plate 47; both the members 46 and 47 being apertured coaxialwith the pole piece 45.

To the plate 47 is secured a fixed contact 48 that cooperates with amovable contact 49 supported by a leaf spring conductor 50 of the formillustrated in the drawing, and that is secured to the leg 43 of themagnet frame by rivets or other devices 51. The spring conductor is soconstructed and mounted with respect to a bimetallic hinge 53, that atension is provided in the leaf spring conductor that tends to urge theconductor into anormal position, consequently the conductor urges thecontact 49 into engagement with the contact 48. In the form illustrated,the contacts 48 and 49 are disposed at one side of the pole piece 45,and substantially over the leg 42 of the magnet frame, so that thespring leaf conductor 50 in making connection with the leg 43 lies overthe central apertures of the contact supporting plate, and also over thepole piece 45. At a point coaxial with the pole piece-a pad 52 isprovided that operates as an engaging piece for an armature rod of theelectromagnet. The spring leaf 50 is attached to the magnet framethrough the olce of a bimetallic hinge 53 secured thereto by a rivet orlike device 54.

The cylindrical pole piece 45 is provided with a 1 carry with it the rod61 when the magnet is energized. A magnet winding 65 is disposed aboutthe pole piece 45, and is insulated therefrom by a dielectric sleeve 66and heads 67 and 68 carried by a nonmagnetic sleeve 69 in frictionalengagement with the pole piece 45.

The winding 65 provides a terminal 70 attached to the terminal clip 26and thus has electrical engagement with the bar 30 and the clip 25. Aterminal 71 at the other end of the winding is attached to the contactsupporting plate 47 and thus has electrical connection with the springleaf conductor 50 through the contacts 48 and 49. From this it will beobserved that if a current source, such as a battery, is connected withthe terminal clip 34, and if work devices are electrically connectedwith the bar 30, that the relay device is then in series with thecircuit as is exemplied by the following tracing.

With the device in its normal position of rest, and for such voltagepressures upon the work circuit as the work devices are designed torespond to, the electrical impulse follows from the terminal member 34through the magnet frame 41 to the rivets 51, where, in the preferredform it makes its way to the spring leaf conductor 50 by means of thebimetallic hinge 53, and thence through the contacts 49 and 48 to theplate 47 where electrical connection is made with the lead 71 throughthe winding 65 to the other lead 70, and thence to the terminal clip 26from Whence'it makes its way to the various work clevvices coupled tothe bridge member 30.

The relative position of the device in the circuit is fully illustratedin Fig. 2, to which reference is now made. The device is normallycalibrated to permit the usual current required by the work devices,such as the lights or other instruments connected in the circuit, tofunction Without response to the voltage pressure they may require.However, if this current demanded by the work devices is exceeded to anyappreciable extent, such as by a short circuit, then the magneticinfluence of the current passing through the magnet winding operatesupon the armature 62 to separate the contacts 48 and 49. The circuit isthen opened and the magnet winding deenergized, lwhich allows thearmature 62, by reason of the spring 63, to return to its normal positonallowing the contacts 48 and 49 to again close. This action continuesrapidly, but the frequency of the vibration is lowered by the use of thenonmagnetic sleeve 69 placed over the core 45. The vibrating actionreduces the current to a value that prevents rapid or excessiveover-heating of the wires, or an excessive drain on the battery, and atthe same time products a rattling sound that gives a warning of a shortcircuit, or over-voltage impression.

Normally the contact tension, or the conductive engagement of the points48 and 49, is only a few ounces and there is some tendency of thesurfaces of the contacts to corrode when the device is not subject toshort circuits, or is subject to disuse. When a short circuit isproduced the contacts are automatically cleaned by the hammering of theone upon the other due to the vibratory action of the electromagnet.However, a short circuit seldom occurs, and the corrosive action on thepoints is suicient in time to prevent the normal flow of currenttherethrough. In consequence thereof the work devices fail to function.Further, by reason of high production in manufacture it frequentlyhappens that the contacting surfaces of the members 43 and 49 are notperfectly flat, but that the conductive engagement thereof is insubstance a pair of contacting points. During normal service thevibration of a car is sometimes sufficient to move one of the contactsfrom its original position on to a portion of the surface of the othercontact that has been oxidized or otherwise corroded, thus establishinga film of insulation between the contact points and preventing a flow ofcurrent therethrough.

The instant invention solves these problems in a novel way as willappear in part from the structural description that has preceded, andits operation will now follow. The normal change in temperature of theatmosphere is made to alter the relation Yof the contacts 48 and 49 fromthe position illustrated in Fig. 3 to that position illustrated in Fig.5, through the agency of the bimetallic element 53. This is accomplishedin the following manner: heat moves the bimetallic element 53 about anarc, from the position shown in dot-and-dash lines to that position asshown in Fig. 5, tending to separate the contacts 48 and 49, but thetension provided in the conductor 50 is sufficient to overcome theaction of the bimetallic element attempting to raise the contact 49 fromcontact 48, consequently the contacts remain in engagement with eachother, thus providing a wiping action across the contacts. Assuming thatthe bimetallic element is made up of a strip of material H having a highrate of expansion, and a strip of material L having a low rate ofexpansion, and is positioned as illustrated in the drawing, then adecrease in temperature operates to move the upper contact 49 toward theleft as viewed in the drawing, at the same time increasing theconductive engagement between the contact points. On the other hand, arise in temperature experienced by the bimetallic element will operateto move the upper contact toward the right hand of the drawing inrelationto the xed contact, substantially as illustrated in Fig. 5, andincidentally decreasing the conductive engagement between the contactpoints. This movement o f the contact 49 over the contact 48 tends tokeep the contacting surfaces clean of corrosion, oxidation or otherdeposits.

In addition to providing the cleaning action, the bimetallic elements ortemperature responsive means also has the effect of automaticallyadjusting the calibration of the device for cold weather drivingconditions. This is desirable inasmuch as the instantaneous currentrequired by cold incandescent lamps is several times the normaloperating current, and, inasmuch as this instantaneous increase incurrent is sometimes suicient to cause enough magnetism in the winding65 to actuate the armature 62 whereby the contacts 48 and 49 would beseparated. Under these conditions when the surfaces of the contacts cometogether again they may not have the same relation, and may be separatedby a film of foreign material which would operate to maintain a break inthe circuit. The temperature responsive means operating at successivechanges of temperature in the region about the circuit controllingdevice operate to keep the pointsof the contacts free from such foreignmaterial, and thereby maintain the device in a high state of eiliciency.

The introduction of the bimetal, also serves another purpose thataffords further protection to the wiring of the circuit and the battery,when the same is short circuited by any means. That is, when a shortcircuit is produced in the work circuit the magnet operates to open thecircuit through the contacts 48 and 49 at rapidly succeeding intervals.This rapid opening and closing of the contacts is accompanied by acertain amount of arcing that develops heat passing along the conductor50 to the bimetal hinge 53. This temperature'change so conductedmanifests in a bending of the bimetallic element 53 suincient to reducethe tension of the spring leaf conductor 50 and thereby varies theconductive engagement between the contact points 48 and 49, or thetension of the spring conductor 50. In response to this, there is acorresponding change in the amount of current flowing in the circuitthrough the contact points.

If the temperature rise becomes excessive, the bimetallic element willoperate to actually separate the contacts, and they will remain apartuntil the bimetal'has cooled sufficiently to restore the normal positionand reaccomplish their conductive engagement, whereupon the points willagain vibrate by reason of the closed circuit until the action of thebimetal will again completely open the circuit. The resultant actiontherefore is suflcient not only to reduce the amount of current carriedby the circuit when the points are vibrating, but also to introduce atime interval sufficient to prevent an injurious rise in temperature inany part of the circuit, and likewise prolong discharge of the battery.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of' the claimswhich follow.

What is claimed is as follows:

l. In a current limiting device, the combination comprising; a pair ofcontacts, one of which is movable; a lever carrying one of the contacts;electromagnetic means for actuating the lever so as to move the movablecontact; and temperature responsive means connecting the lever with astationary part and so constructed and arranged as to move said lever ina direction such as to cause the movable contact to move across the faceof the stationary contact while in engagement therewith.

2. A current limiting device comprising in combination; a magnet relayproviding a pair of "contacts, one of which is movable; a leaf springconductor carrying said movable contact, said spring conductor beingconstructed and arranged so as to urge said contact into engagement withthe other contact; a temperature responsive means connecting the leafspring conductor with a stationary part, said means operable undercertain circuit conditions to move said conductor slide over the face ofthe stationary contact while in engagement therewith. r

3. Ina current limiting device the combination comprising; a pair ofcontacts normally in conductive engagement, one of which is movable; alever carrying one of the contacts; means operable to separate thecontacts; and temperature responsive means connecting the lever with astationary part and operable in response to a predetermined temperatureto shift said lever in a direction such as to cause the movable contactto slide across the face of the other contact for varying the conductiveengagement of said contacts while in closed position to `maintain theengaging surfaces thereof free from insulating films.

4. In a current limiting device the combination comprising; a pair ofcontacts one of which is movable; a support for one of said contacts;electro-magnetic means for actuating the support so as to move themovable contact; temperature responsive means connecting said supportwith a stationary part and operable to move said support in a directionto cause said movable contact to move across the face of the stationarycontact while in engagement therewith.

5. In a current limiting device the combination comprising; a pair ofcontacts, one of which is movable, a lever carrying one of saidcontacts; means operable to separate the contacts in response to certainelectrical potential; bi-metallic means connecting said lever with astationary part and operable in response to certain other electricalpotential for moving said lever to cause said movable contact to moveover the other contact to vary the conductive engagement thereof.

6. A switch, comprising in combination; a pair of contacts, one of whichis movable; a lever carrying the movable contact; means for moving thelever laterally to separate the contacts; and temperature responsivemeans connecting the lever with a stationary part and so constructed,and arranged as to move the lever in a direction such as to cause themovable contact to move across the face of the stationary contact whilein engagement therewith.

'7. A switch, comprising in combination; a pair of contacts, one ofwhich is movable; a leaf spring conductor carrying the movable contactand adapted to urge said contact into engagement with the other contact;means for moving the leaf spring laterally to separate the contacts; abimetallic hinge connecting the leaf spring with a stationary part, saidhinge operable under certain circuit conditions to move the leaf 'springin a direction to cause the movable contact to slide over the face ofthe second mentioned contact while in engagement therewith.

8. A switch comprising in combination; a pair of contacts, one of whichis movable; a resilient member carrying the movable contact and urgingsaid contact into engagement with the other contact; means for movingthe resilient member to separate the contacts; andf temperatureresponsive means connecting'the resilient member with a stationarymember andoperable in response to c ertain temperature conditions tochange the positionof theresilient member so as to cause themovablejcontactuto slide across ythe face of the in a direction to causethe movable contact toother contact while Ain engagement therewith.

j9.j Af'switch comprising in combination; a pair of contacts, one ofwhich is movable; a lever carrying the movable contact; means for movingthe lever laterally rto separatethe contacts; a temperature responsivemeans connecting the lever with a stationary part, said means operableunder certain circuit conditions to shift said lever to cause themovable contact to slide over the surface of the stationary contactwhile in engagement therewith to free the engaging surfaces of saidcontacts of insulating films.

HARRY C. DOANE.

